Nuclear quadrupole resonance

About: Nuclear quadrupole resonance is a research topic. Over the lifetime, 3531 publications have been published within this topic receiving 38801 citations. The topic is also known as: Nuclear quadrupole resonance spectroscopy & NQR.

Nuclear quadrupole coupling constants from the Gaussian density-functional method

Abstract: ~Received 29 September 1995! The reliability of density-functional theory in predicting nuclear quadrupole resonance ~NQR! frequencies and nuclear quadrupole coupling constants was tested for a series of straight-chain chloroalkenes ~vinyl chloride, 2-chloropropane, cis- and trans-1-chloropropene, cis-dichloroethylene, and tetrachloroethylene!. The calculations were performed using the linear combination of Gaussian-type orbitals local-spin-density method and the generalized gradient approximation. The calculated NQR frequencies are in good agreement with experimental data. Less satisfactory agreement is found in the prediction of quadrupole coupling constants. The results show that the calculated NQR frequencies and nuclear quadrupole coupling constants can be used to study the electron distribution in molecular systems. @S1050-2947~96!06905-3# PACS number~s!: 31.15.2p I. INTRODUCTION

Observation of Secondary Magnetic Transition in Teragonal YBa2Cu3Ox (6.1≤x≤6.4)

Abstract: Temperature dependence of nuclear resonance spectra for the chain Cu(1) and the plane Cu(2) sites was investigated in the oxygen-deficient tetragonal YBa 2 Cu 3 O x (6.1≤ x ≤6.4). The divergence of the spin-echo decay rate for the NQR at the Cu(1) site was observed at about 20 K, irrespective of the oxygen concentration, x , in x ≥6.2. Below this critical temperature, only the NQR line broadening becomes significant without any resonance shifts. The spin-echo decay rate for the NMR at the Cu(2) site in the sample with x =6.2 also increases divergently when the temperature is raised to the critical temperature. These facts directly indicate the secondary transition associated with the moments on the Cu(2) sites at about 20 K, which is well below the Neel temperature. Some discussions are included for the magnetic structure below the transition temperature.

Interpretation of nuclear quadrupole resonance spectra in doped La2CuO4

Abstract: The nuclear quadrupole resonance (NQR) spectrum of strontium-doped La2CuO4 surprisingly resembles the NQR spectrum of La2CuO4 doped with excess oxygen, both spectra being dominated by a main (A) peak and one principal satellite (B) peak at similar frequencies. Using first-principles cluster calculations, this is investigated here by calculating the electric field gradient (EFG) at the central copper site of the cluster after replacing a lanthanum atom in the cluster with a strontium atom or adding an interstitial oxygen to the cluster. In each case the EFG was increased by approximately 10% leading unexpectedly to the explanation that the NQR spectra are only accidentally similar and the origins are quite different.

Density Functional Theory based Electric Field Gradient Database

Abstract: The deviation of the electron density around the nuclei from spherical symmetry determines the electric field gradient (EFG), which can be measured by various types of spectroscopy. Nuclear Quadrupole Resonance (NQR) is particularly sensitive to the EFG. The EFGs, and by implication NQR frequencies, vary dramatically across materials. Consequently, searching for NQR spectral lines in previously uninvestigated materials represents a major challenge. Calculated EFGs can significantly aid at the search inception. To facilitate this task, we have applied high-throughput density functional theory calculations to predict EFGs for 15187 materials in the JARVIS-DFT database. This database, which will include EFG as a standard entry, is continuously increasing. Given the large scope of the database, it is impractical to verify each calculation. However, we assess accuracy by singling out cases for which reliable experimental information is readily available and compare them to the calculations. We further present a statistical analysis of the results. The database and tools associated with our work are made publicly available by JARVIS-DFT ( this https URL ) and NIST-JARVIS API ( this http URL ).